Scuba Regulators Explained - Force-E Scuba Centers

Scuba Regulators Explained

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  • By Scott Hurley
  • Posted in Scuba Gear
Scuba Regulators Explained

Do you know how your scuba regulator works?

A scuba regulator is your life support system while you are diving. It is the most important piece of dive gear as it connects your air supply in your tank and it allows you to breathe from the tank underwater. Have you ever wondered how it really works? One of our gear experts will break it down for you...


How does first stage portion of a scuba regulator work?


Scuba regulators perform the critical job of delivering breathable gas from pressurized air tanks to you using two stages.  The air in a scuba diving tank is usually filled to 3,000 psi in standard aluminum 80 cubic feet tank.  The regulator’s first stage which attaches to the tank valve lowers the tank pressure to an intermediate working pressure (about 120-150 psi), this air then travels through the regulator hose to the regulator’s second stage.  The first stage part of the regulator consists of two air chambers that are separated by a poppet valve.  When the regulator is not pressurized on a tank this poppet valve is open.  When the regulator is connected to a tank, then air from the scuba tank flows into the first chamber, through the poppet valve, and into the second chamber.  The poppet valve between the two chambers stays open until the air in the second chamber reaches the regulator’s intermediate pressure.  Once, the air in the second chamber reaches the intermediate pressure, the poppet valve closes, preventing high-pressure air from the tank flowing into the second chamber. When you inhale, air from the second chamber is released through the hose to the second stage.  As the air in the second chamber is released, the pressure drops in the second chamber, allows the poppet valve between the two chambers to open.  This process then restarts as air flows from the first chamber into the second chamber until the pressure in the second chamber rises to an intermediate pressure that then forces the poppet valve to close. 


Types of First Stages

Regualtor Diagram 1

Regualtor Diagram 2

















The first stage portion of scuba regulator can rely either on a piston or diaphragm to accomplish lowering the tank pressure to an intermediate pressure.  Inside the first stage, there is a high-pressure poppet valve, seat assembly and a spring.  Atomic Z3 regulator has a piston first stage that uses a piston that moves up and down against a large heavy spring.  When the regulator is pressurized by opening the tank valve, the piston moves and allows the air to pass the high-pressure seat.  When the pressure inside the regulator reaches the intermediate pressure, then the poppet valve closes against the seat and the air stops flowing.  Aqua Lung Titan regulator has a diaphragm first stage that uses a thick piece of rubber (diaphragm) that is pressed up against a metal pin seated on a spring and then the hard plastic high pressure seat.  There is another spring pushing on the diaphragm from the opposite direction holding it closed.  When the regulator is pressurized by opening the tank valve, the spring against the plastic high pressure seat opens, and gas flows into the second chamber until the intermediate pressure is reached.  Then the regulator closes and this process repeats as you breathe.  


Unbalanced, vs. Balanced First Stage


Regualtor Diagram 3

Regualtor Diagram 4

















Tusa RS1207 regulator has an unbalanced first stage that experiences  different pressures on each end of its poppet valve-spring assembly.  Unbalanced first stage regulators are unable to keep the intermediate pressure consistent due to changes in depth and lower tank pressures, thus increasing breathing resistance.  Apeks AT20 regulator has a balanced first stage that routes air to both sides of the poppet valve-spring assembly, so that it gives unvarying intermediate pressure so that breathing resistance is the same given the external conditions.  There is another class of first stage regulators called “overbalanced” that slowly increases the intermediate pressure as ambient pressure increases such as when you descend deeper instead of the intermediate pressure being constant. Aqua Lung Leg3nd MBS regulator provides a unique over-balanced, diaphragm design that results in superior performance at depth. 


How does second stage portion of scuba regulator work?


Regualtor Diagram 5

The regulator’s second stage which is the part that goes into your mouth.  The second stage reduces air from the intermediate pressure to ambient pressure so that you can safely breathe.  An unbalanced second stage consists of a single air chamber with a valve in the inlet fitting for the hose from the first stage and a spring, much like the first stage.  This valve stays closed except when you inhale and then it is triggered to open by your breathing effort.  The second stage uses a flexible silicone diaphragm to seal water out and air inside of the second stage.  There is a lever that rests against the diaphragm that operates the valve in the inlet fitting.  When you inhale, it lowers the air pressure inside the second stage by you taking some of the air into your lungs.  This allows water outside to push the diaphragm in slightly, which pushes on the lever that opens the valve, and allows air to rush in until it equals the ambient pressure.  The second stage portion of scuba regulator can also be pneumatically balanced which is accomplished by routing intermediate pressure air to the backside of the valve to help counteract the force of the spring inside the second stage.  This allows the valve to open with much less effort, making the regulator easier to breathe, such as the higher ambient pressure experienced at greater depth.  Apeks MTX-RC regulator has super-smooth breathing experience due to the pneumatically balancing of the second stage, that lets you explore more.    


Scott Hurley
Scott Hurley is part of the Force-E Team working as store staff member since 2002. He works part-time at the Riviera Beach store and full-time as Biological Scientist for Florida Atlantic University Harbor Branch on a project supporting a real-time water quality monitoring network. HIs passion was realized shortly after getting scuba certified so that he could study the underwater world.